Reciprocatory machines

ABSTRACT

A reciprocatory machine having a cylinder defining with at least one piston a working chamber. Each piston is reciprocable in the cylinder by a respective crankshaft. The machine has intake and exhaust ports disposed at opposite ends of the working part of the cylinder and has respective valves additional to the pistons for opening and closing the ports. The valves are driven by the crankshaft(s) and have provision for adjusting the timing relationship between the displacement of the crankshaft(s) and the valves and thereby the timing relationship between the respective valves. The location of the ports at opposite ends of the working part of the cylinder permits considerably greater adjustment of the timing than is possible with conventional closely spaced porting arrangements. The machine preferably operates as a two-stroke internal combustion engine but may also operate as a pump or compressor.

This is a continuation Ser. No. 07/337,764 filed Mar. 28, 1989, nowabandoned.

This invention relates broadly to reciprocatory machines but provides,in a particular aspect, an internal combustion engine generally having atwo-stroke cycle and adaptable to spark ignition or compressionignition.

Known internal combustion engines have proven very difficult to tuneproperly. Nevertheless, variable valve timing for conventional and otherengines is well known and is generally performed by adjusting therotational relationship between the crankshaft and the valve camshaft.Inbuilt provision for timing adjustment between the crankshaft and thevalve camshaft has been proposed, for example, in British PatentSpecification 2109858 which provides separate camshafts for the intakeand exhaust valves and adjustment of the respective camshafts in amanner which is said to produce any desired change in the overlapping ofthe valve timing between the intake and exhaust valves.

In other cases where the ports are valved by respective opposed pistons,it has been proposed to provide for adjustment of the phase relationshipbetween the pistons Such arrangements are suggested in German patent616,451, in U.S. Pat. Nos. 2,113,480 and 2,401,188 and in British patent584,783. In the latter case, a turbocharger is coupled to the intakeport. In these engines, adjustment of the piston timing, for example inresponse to engine load, is marginally effective to vary the compressionratio and does inherently alter the valve timings but is clearlyincapable of providing independent adjustment of valve timing. Moreover,altering the phase relationship between the pistons impairs or reducesthe naturally very high level of dynamic balance within each cylinderthat occurs when the crankshafts and pistons are in phase.

It is an object of the present invention to alleviate the aforementioneddisadvantages of reciprocatory machines.

In accordance with the invention, the present invention has realizedthat difficulties experienced in achieving valve timing adjustment ininternal combustion engines stem from the location of the intake andexhaust ports and/or associated valves and particularly from their closeproximity in most conventional engines, especially four-stroke enginesThus, in most cases both the intake and exhaust ports are located in thecylinder head close to top dead center where space is at a premium andany adjustment other than minimal to the timing relationship between thepiston and the valves may cause the piston and the valves to interfere,with consequent damage to the engine. If adjustment is possible to thetiming relationship between the valves for the intake and outlet ports,the adjustment is also limited by the need to avoid interference betweenthe valves.

The close proximity of the intake and outlet valves also leads to thepossibility of reverse or spill flows of the inlet and exhaust gasesoccurring and any adjustment in the valve timing must be sufficientlysmall to avoid undesired reverse or spill flows.

The inventor has further appreciated that adjustment of the phaserelationship between pistons also acting as valving means is anunsatisfactory device for achieving the real object - adjustment of thephase relationship between the valving means.

The present invention therefore provides a reciprocatory machinecomprising means defining a working chamber, at least one pistonreciprocable within the chamber, displaceable means associated with thepiston or pistons and adapted to translate reciprocating movement of thepiston or pistons into rotational movement or vice versa, intake andexhaust ports for the working chamber and respective valve means forsaid ports additional to said pistons, and wherein said intake andexhaust ports are disposed at or adjacent to respective ends of theworking chamber and means is provided for adjusting the timingrelationship between the displacement of the translating means and thevalve means and thereby the timing relationship between the respectivevalve means.

Preferably the reciprocatory machine includes ignition means operable inthe working chamber whereby the machine comprises an engine, preferablybut not necessarily operable on a 2-stroke cycle. Alternatively theinvention may be adapted to, for example, a compressor.

By the present invention it is possible to provide a substantiallyinfinite variation of valve timing within a wide range by virtue of thespacing of the intake and outlet ports allowing for more precise controlof the inlet and exhaust flows and, if desired, essentially a totalelimination of reversed or spill flow of the inlet and/or exhaust gases.Furthermore, the separation of the valve means at or adjacent respectiveends of the working chamber avoids the risk of their colliding, whilethe risk of collision between the piston and one of the valve means maybe alleviated by providing only small or no adjustment of that valvemeans with the other valve means being fully adjustable or by using assaid one valve means a type of valve with which collision is unlikely tooccur, such as a sleeve valve. Generally however, the invention isapplicable to various combinations of types of valve means, includingsleeve valves, poppet valves and rotary distributor type valves, andpreferably the intake and exhaust valve means are both adjustable fortiming. Examples of engines in which the present invention may bereadily used are the Detroit Diesel Engine having a poppet exhaust valvein the cylinder head and inlet ports in the cylinder wall near BottomDead Center, and the Ricardo sleeve valve engine.

Substantially infinite variation over a wide range of the valve timingmay permit substantial variation of inlet timing, exhaust timing,effective compression ratio, effective expansion ratio, exhaust "blowdown" period and supercharging period. This range of variation maypermit a total change in character of the reciprocating machine from,for example, a racing car engine to a low horsepower engine for a roadgoing family sedan. Advantageously the valve timing is adjustable duringoperation of the machine and by use of duplex cams, eccentrics and/orother suitable operating mechanisms, variation of timing may be effectednot only continuously but within each cycle.

By the term "effective compression ratio" we mean the volume containedin the working chamber at the first moment at which the working chamberbecomes sealed during a cycle divided by the minimum volume contained inthe working chamber during the cycle, and by the term "effectiveexpansion ratio" we mean the volume contained in the working chamber atthe first moment at which the working chamber is opened to exhaustduring a cycle divided by the minimum volume contained in the workingchamber during the cycle.

One particular advantage of the invention, and in particular of theability to finely control valve timing, is to render 2-stroke enginescapable of optimum conjunction with a turbocharger. The benefits ofturbocharging are well known and have been successfully obtained forsome years with 4-stroke engines. However, it has generally been foundvery difficult to successfully apply turbocharging to 2-stroke engines,due largely to the typical conflict between the engine's general demandfor inlet manifold pressure to rise as a cube function of speed and theturbocharger's quite different discharge pressure characteristic, andalso due to a 2-stroke engine not being able to provide a positivenaturally occurring inlet stroke such as normally occurs in a 4-strokeengine.

These problems are met by the invention. The provision for adjustmentbetween the two valve means permits two notable temporary timingrelationships, as follows:

(i) when a warm re-start is required, early opening of the exhaust valvewill allow use of the pressure and/or thermal and/or kinetic energy ofthe hot residual gases within the cylinder to drive the turbocharger andso facilitate the refilling cycle.

(ii) for starts in general but especially cold starts, the valve timingcan be adjusted to raise the compression ratio, lowering it again forsubsequent running operation.

Generally the valve means will be driven by the translating means, whichmay comprise, for example, one or more crankshafts, and the drive meansmay comprise an internally toothed belt, commonly known as a timingbelt, or a gear train, plus crank and pin or eccentric and followermechanisms. In a preferred embodiment, the drive means to the or eachadjustable valve includes a helical gear train and the adjusting meanscomprises means for varying the phase change across the gear train. Thegear train for the or each adjustable valve may include respectivehelical gears on the translating means and on a drive shaft for thevalve, and interposed helical gear means meshing with said helicalgears, with the gear means being linearly movable parallel to the axesof the helical gears.

In the early years of internal combustion engines, poppet valvingexperienced difficulties with excessive noise and a tendency to induceboth detonation and pre-ignition. An alternative was sleeve valving,which was used in a number of early commercial engines, particularlyaero engines. The history of sleeve valve engines is well summarized inthe standard text "The High-Speed Internal Combustion Engine" by SirHarry Ricardo (published by Blackie & Son Limited, London) who himselfbuilt a number of successful long-life sleeve valve engines and carriedout extensive research regarding their performance and optimum design.

Sleeve valve engines were found to have a number of significantadvantages. Their mechanical efficiency and fuel consumption wereimpressive and in part arose from the unexpectedly low frictional lossesat the interfaces between the reciprocating sleeve, typically a nitridedsteel, and the cylinder barrel and piston. Provided the sleeve wasreciprocated both longitudingly and circumferentially, there wasexcellent lubrication between the sleeve and the cylinder barrel. TheRicardo engines operated for many hours without any significant problemsin the sleeve or piston motion. The engines were quiet and it was foundthat the piston temperature in a liquid-cooled sleeve valve engine wasactually a little lower than in a poppet valve engine of similarcapacity and output, apparently because the moving oil film between thesleeve and cylinder wall was a very efficient convector of heat awayfrom the piston. Because the cylinder head was unencumbered by ports andvalves, one had complete freedom as regards the form or capacity of thecombustion chamber.

These advantages were especially applicable to 2-stroke engines, butthere were also found to be some significant disadvantages whichmitigated against the widespread commercial application of 2-strokesleeve valve engines, particularly given that the major objectionablefeatures of early poppet valve engines had later been resolved. Ricardosaw two significant difficulties which he summarized at page 387 of histext (cited above):

"1. The nitrided sleeves have a life of probably 2000 to 4000 hoursbefore wear of the top end of the sleeve renders them unservicable. Thisis long enough for military aircraft, but not nearly long enough forordinary commercial duties. Some means will yet have to be found forreducing the rate of wear in this zone.""2. Although the open-endedsleeve appears to seal perfectly under all operating conditions, it doesnot provide a complete seal when starting from cold, and some means,such as the injection of a little thick oil, must be applied to enablethe compression ignition version to start from cold: this is rather anobjectionable feature."

The wear of the top end of the sleeve arose from exposure of this partof the sleeve to the full flow of exhaust gases and/or mechanicalinterference with the upper part of the cylinder barrel or head.Secondary disadvantages of the sleeve valve engine were the bulky andexpensive re-entrant head, known as a junk-head, which gave rise towasteful heat losses and, in air cooled applications, was difficult toadequately cool.

In the case of 4-stroke sleeve valve engines, the two problems noted byRicardo did not apply but the presence of the junkhead was still asignificant obstacle to commercial development.

One solution to those problems not appreciated even by Ricardo butdisclosed in British Patent Specification 497,300 to Porkman, and inBritish patent 1,015,189 to Lindsay, was to adapt the fundamentals ofsleeve valving to an opposed piston engine, that is to provide a pair ofopposed pistons with respective sleeves providing valves for the exhaustand intake ports. There were a considerable number of successful andcommercial opposed piston engines, of which typical examples are JunkersJumo, Rootes Diesel and Napier Deltic engines but all relied upon pistoncontrolled valving. So far as the applicant is aware, an opposed pistonengine of Porkman's or Lindsay's design was never commercialized andsleeve valved engines have remained only an historical curiosity sincethe end of World War II despite their advantages as noted by Ricardo. Itis believed that the present invention will encourage those advantagesto be realized, both in non-opposed and opposed piston form.

Referring now particularly to a sleeve valved engine, the or each sleeveis preferably driven in a reciprocatory motion which is bothcircumferential and longitudinal. The stroke of the circumferentialmotion is preferably at least 20% of the stroke of the longitudinalmotion.

In the case of two opposed pistons in the working chamber, and sleevevalving in the form of respective sleeve valves for the spaced exhaustand intake ports, the separate sleeves are advantageously reciprocableabout the respective pistons. Preferably, respective crankshafts areprovided for the two pistons, and the sleeves are reciprocable byseparate drive means from the respective crankshafts. The crankshaftsare preferably directly coupled by an internally toothed belt, and thedrive shaft to the load is preferably parallel or co-axially coupled toone or both of the crankshafts.

The intake port is advantageously coupled to a supercharger, and mostadvantageously to a turbocharger mounted to be driven by products fromthe exhaust port.

Two embodiments of the invention will be further described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a multi axial somewhat diagrammatic cross-section of a2-stroke opposed piston sleeve valved engine in accordance with theinvention, with the pistons shown close to top dead center;

FIG. 2 is an enlargement of one end of the engine of FIG. 1; and

FIG. 3 is a view similar to FIG. 2 but showing the one end of the enginemodified to operate alone.

Referring to FIGS. 1 and 2, the illustrated opposed piston 2-strokeengine 8 is substantially symmetrical about a transverse median planeA-A and includes a cast engine block 9 which encompasses a cylindricalbarrel 12, defining a working chamber and crankcases 14, 15 with coverportions 35. The engine further includes respective crankshaftassemblies 16, 17, and a pair of opposed pistons 18, 19 coupled to thecrankshaft assemblies 16, 17 by connecting rods 20, 21 for oppositereciprocation within the working chamber timed by an internally toothedbelt 24. Barrel 12 and crankcase assemblies 14, 15 are shown forconvenience as a single casting but this may be varied according tocircumstances. FIG. 1 illustrates the crankshafts in phase and thepistons at top dead center, inwardly of respective rings of ports 26, 27in cylinder barrel 12. The crankshafts may of course be set out of phaseas desired, for example to achieve improved air scavenging in two-strokemode. Ports 26, 27 open to respective annular manifolds 25, 29, which inoperation comprise an intake manifold and an exhaust manifold, and whichcommunicate in turn with ducts 25a, 29a. The exact physical structure ofthe manifolds and associated ducts is not detailed, being indicatedschematically only in FIG. 1. Intake duct 25a is coupled to the outletof a turbocharger assembly 90 including a blower 92 driven by a turbine94. Turbine 94 is in turn powered by exhaust gases directed along duct29a.

The combustion chamber 13a substantially comprises a pair of radiusedcavities 28 in the heads 30, 31 of pistons 18, 19. As shown the cavities28 are spherically radiused, but in alternative configurations thepiston heads, or discrete crowns if desired, may be flat or convex. Forspark ignition and/or injection access to the combustion chamber,cylinder barrel 12 is provided with peripherally spaced ignition ports32, and piston heads 30, 31 with registering grooves 32a. Injectiondevices 1,1 for compression ignition are illustrated in this case but itis emphasized that spark plugs may be substituted as desired.

The crankcase and crankshaft assemblies are substantially identical andit is therefore proposed to describe in detail only those at the upperend of the engine as seen in FIG. 1. This end is enlarged in FIG. 2.Crankshaft assembly 16 includes a pair of co-axial crankshafts, a drivecrankshaft 40 and a timing crankshaft 41. The two are supported incrankcase 14 and crankcase covers 35 by spaced roller bearings 42, 44.The crankshaft assembly is coupled to the piston in a substantiallyconventional arrangement including a tubular crankpin 46, a gudgeon pin50 retained in a matching or transverse bore 51 in piston 18, andconnecting rod 20 which receives crankpin 46 and gudgeon pin 50 withinrespective roller cages 54, 55.

The two timing crankshafts 41 are keyed through crankshafts 40 torespective pulleys 60, 61 (FIG. 1) for timing belt 24. A taperedmounting is used as illustrated at 40a not only for the usual reason ofensuring a secure mounting but in this case also to permit tensioning ofthe timing belt in the absence of any idler pulley for such purpose.

Cylinder barrel 12 is fitted with a pair of similar elongate sleevevalves 10, 11 which, by virtue of spaced rings of apertures 26a, 27a, inthe sleeves, provide valving for ports 26, 27 and are reciprocable aboutthe respective pistons 18, 19. Sleeves 10, 11 may be formed in castiron, nitrided steel or other suitable materials such as ceramics orhigh performance plastics. They make a good tolerance fit within thecylinder barrel and are each free to reciprocate both longitudinally andcircumferentially. O-ring seals are provided where shown, for example at10a, 11a on the intermediate walls of the cylinder barrel and on thecylindrical surfaces of the pistons In operation, a thin film of oil issupplied and maintained between the sleeves and the barrel and it is forthe purpose of maintaining proper distribution of this film that thecircumferential component of the oscillation is primarily necessary.

Sleeves 10, 11 are reciprocable from the respective crankshafts 40 bymeans of separate helical gear trains 68 which are substantiallyidentical and which are fitted with means for adjusting the timingrelationship or phase between the respective pistons and the valving ofthe associated ports by the sleeves, and thereby the timing relationshipbetween the sleeves in accordance with the present invention. Each geartrain 68 comprises respective helical gears 72, 73 on crankshaft 41 andon a crank 74. These gears mesh with an intermediate helical gear 71which is both slidably and rotatably mounted on an interposed stud 75.As the illustrated engine is configured for 2-stroke operation, gears72, 73 are in 1:1 ratio.

Crank 74 is supported in roller bearings 74a and has a socket 76 housinga spherical bearing 78 for a spigot 80 projecting laterally integrallyfrom the sleeve 10. It will be appreciated that this arrangementachieves the required two component motion: the motion is optimised forlubrication purposes, as described above, if the stroke of thecircumferential component of the reciprocatory motion is at least 20% ofthe stroke of the longitudinal component.

Phase adjustment is achieved by way of a slidable push-pull rod 77 whichseats in an annular groove 81 of a boss 82 on intermediate gear 71. Rod77 slidably projects through a gear case cover 79: slight movement ofgear 71 along stud 75 will itself cause relative rotation of the gears,because they are helical gears, and thus an alteration of the phasebetween crankshaft 40 and crank 74. This in turn will vary the timingrelationships mentioned above. This arrangement permits infinite timingphase adjustment over a 180° range.

Instead of driving each sleeve via a crank 74, a camshaft may beemployed. This affords the additional advantage that the timingrelationship(s) may be varied, not only by adjusting rod 77, but also,by utilizing a cam of selected shape, within each stroke of the engine.

Rod 77 may be arranged for manual control, or for automatic control inresponse to, e.g., the monitoring of intake manifold pressure, enginespeed, road speed, throttle setting and torque output.

Sleeves 10, 11 are provided with complementary scallops 32b, whichregister at the required times with injection ports 32 and pistongrooves 32a. Apertures 26a, 27a in the sleeves co-operate as requiredwith barrel ports 26, 27. It is not thought necessary to provide anyspecific detail regarding the port configuration as it will depend,inter alia, on the mode of operating the engine and on the air flow andthe range of phasing characteristics desired. Considerations in relationto timing adjustments under different engine load conditions are alsowell known as provision of such adjustments is a known art.

An important preferred feature of the engine disclosed in FIGS. 1 and 2which facilitates smooth and trouble-free operation is the use of timingbelt 24 as a direct drive coupling between the crankshafts. Mostadvantageously for the particular application, this belt is preferablyan advanced belt of the HTD design marketed by the UniRoyal Company.Such belts would also advantageously be employed to couple the outputshaft to load.

It will be appreciated that the engine illustrated in FIGS. 1 and 2 mayinclude other modifications or adaptations in accordance with the modein which it is operated and with standard principles of engine design.For example, other forms of supercharging, e.g. Kadency and/orconventional, positive displacement and/or mechanically drivencentrifugal superchargers may be employed. Established sleeve valveporting principles can be applied to take advantage of the porting inboth barrel and sleeve, of the two component motion of the sleeve, andof the lack of direct contact between the piston rings and the barrelports.

It will further be seen that both of the primary objections of 2-strokesleeved valve engines noted by Ricardo and quoted above are overcome:there is no longer any relatively short-term wear of the sleeve ends dueto exposure to full flow of exhaust gases and there is no longer anyproblem with lack of sealing at an open-ended sleeve when starting fromcold. The outer sleeve ends of the engine of FIGS. 1 and 2 lie in thecrankcases and the inner ends are surrounded by the cylinder barrel andare thereby neither exposed to flow of exhaust gases nor in need ofsealing at start-up. This also allows full advantage to be taken of oneof the useful features of sleeve valve engines, the self compensatingrelationship between the size of the sleeve to barrel gap and the rateof heat transferred across the gap. For example, when the tolerance issubstantial, heat transfer from the piston through the oil film isretarded which results in thermal expansion of the sleeve to reduce thegap until a balance occurs between the rate of heat dissipation acrossthe film and the thermally determined diameter of the sleeve.

Elimination of the junkhead means elimination of an expensive, high heatloss component and, moreover, of a component which was difficult to aircool because of its substantial re-entrant bulk. In this latter respect,it is interesting to note the very expensive and detailed compositecopper cooled head produced by the Bristol Aeroplane Company to resolvethe problem of air cooling the junk head.

By adapting the opposed piston configuration to sleeve valving in theengine of FIGS. 1 and 2 it has been possible to not only overcomeoutstanding objections to sleeve valve engines, but to obtain foropposed piston engines the significant known advantages of sleevevalving. In particular, the mechanical efficiency and fuel consumptionare substantially improved relative to prior opposed piston engines, andthe weight to power ratio is markedly enhanced. Thus, one of theobjections to opposed piston engines in certain key applications, theirsomewhat troublesome dimensional configuration, can be overcome in thatthe opposed piston engine can be reduced to a very compact size for agiven power output.

The ability to selectively vary the timing relationship between eachsleeve and the associated piston, makes it possible to obtain infinitevariation over wide ranges of effective compression ratio, effectiveexpansion ratio, timing, and volume of the working space. Thesevariations are not merely possible from cycle to cycle but within eachcycle, allowing the control system to be promptly responsive to changesin the engine's load requirements. This flexibility is valuable inparticular for 2-stroke operation and is to be contrasted with the fixedcompromise timing settings in most conventional engines. The engine canwork and be matched to a variable torque load via a simple transmission:the modern practice to achieve optimum efficiency load matching by wayof a continuously variable torque transmission may be largely supersededby the utilization of the engine itself. The provision of spaced intakeand exhaust valves 26 and 27 in the engine has further advantages. Forone, it renders practical the avoidance of reverse or spill flow whenvarying the effective compression ratio and/or effective expansionratio. This is not possible with either an opposed piston engine withconventional valving or the modern poppet valve engine.

Variation of the valve timing in accordance with the invention permits amost versatile turbocharged 2-stroke engine. Conventional 2-strokeengines are not well-suited to supercharging in general and even less soto turbocharging. Even where turbocharging has been provided, it has notbeen possible to rely on the turbocharger to adequately provide inletair to the engine under starting conditions or for significant parts ofthe engine's load speed curve and a separate mechanical supercharger hasbeen required to overcome these deficiencies.

In cases where turbocharging of 2-stroke diesel engines has beenattempted, a separate external mechanical blower has been required forstarting purposes.

The inventive engine, in contrast, permits turbocharging of a 2-strokeengine under the full range of operating conditions and eliminates theneed for a separate mechanical supercharger. For example when a warmre-start is required, early opening of the exhaust valve will allow useof the pressure and/or thermal and/or kinetic energy of the hot residualgases within the cylinder to drive the turbocharger and so facilitatethe refilling cycle. For starts in general but especially cold starts,the valve timing can be adjusted to raise the compression ratio,lowering it again for subsequent running operation. Under all loadconditions, it is possible to vary the inlet and/or exhaust timing so asto overcome the inherent incompatability of the engine's air demandcharacteristics and the turbocharger's output characteristics, and togenerally tune or modify the engine's characteristics to the prevailingrequirements.

The ability to vary the volume of the working space, a consequence ofthe invention already noted, allows the engine to be run for more of thetime at a brake mean effective pressure which provides high thermalefficiency. In other words, the engine output is then significantlycontrolled by modifying its volume rather than its brake mean effectivepressure away from an efficient condition.

It will be noted that the described arrangement affords near perfectprimary and secondary balance within each cylinder. In contrast, aspreviously mentioned, the known practice of altering the phaserelationship between the pistons in an attempt to alter compressionratio, impairs this very high level of dynamic balance.

FIG. 3 illustrates the half engine of FIG. 2 modified to operate aloneand since the operation of the engine 108 is substantially identical tothe operation of the half engine in FIG. 2 its manner of operation willnot be described again except in relation to its differences.

The engine block 9 in FIG. 3 is modified to define a combustion head 110with apertures 112 and 114 therein to receive an injector or sparkingplug illustrated schematically at 116 and a poppet valve 118. The poppetvalve is also illustrated schematically in the open position but maytake any of a number of known forms which are not believed to requiredetailed description. Furthermore the drive mechanism for the poppetvalve 118 is not illustrated and may be non-adjustable in accordancewith generally standard engine practice. Alternatively, the poppet valve118 is preferably adjustable as to its timing and such adjustability maybe provided by for example the means illustrated in British PatentSpecification 2109858. Alternatively, the adjustment means describedherein for use with the sleeve valve 10 may be duplicated and adapted tothe drive means for the poppet valve. Thus the crank 74 may be connectedvia a gear train or belt to a camshaft having an eccentric fordisplacing the poppet valve against the bias of a spring. Adjustment ofthe helical gear 71 may change the phase of the poppet valve.

Other modifications, alterations and advantages applicable to the enginedescribed with reference to FIGS. 1 and 2 may be applied to the engine108.

Although the invention has been described with reference to an internalcombustion engine, the principles of the invention are also applicableto other forms of reciprocatory machines such as pumps or compressors.

I claim:
 1. A reciprocatory machine adaptable as a 2-stroke enginecomprising means defining a working chamber, at least one pistonreciprocable within the chamber, displaceable translating meansassociated with the piston and adapted to translate reciprocating motionof the piston into rotational movement or vice versa, intake and exhaustports for the working chamber and respective intake and exhaust valvemeans for said ports distinct from said at least one piston, and meansfor causing said respective valve means to cyclically operate inresponse to said reciprocating motion of the piston, wherein at leastone of the valve means comprises a sleeve valve reciprocable within saidworking chamber about said at least one piston and wherein said intakeand exhaust ports are disposed at or adjacent to opposite ends of theworking chamber respectively and means are provided for effectingindependent adjustment of the timing relationship between the cyclicoperation of each of the intake and exhaust valve means and thedisplacement of the translating means including independent adjustmentof the timing of both opening and closing of each of the intake andexhaust valve means, and thereby to adjust the timing relationshipbetween the cyclic operation of the respective valve means.
 2. Areciprocatory machine according to claim 1 wherein the valve means forthe intake and outlet ports are driven by respective drive meansincluding a helical gear train and said adjusting means comprises meansfor varying the phase angle across the gear train.
 3. A reciprocatorymachine according to claim 2 wherein said gear train for each valvemeans includes respective helical gears on the displaceable means forthe or each piston and on a drive shaft for the valve means, andinterposed helical gear means meshing with said helical gears, said gearmeans being linearly moveable parallel to the axes of said helicalgears.
 4. A reciprocatory machine according to claim 1, 2 or 3 whereinsaid intake port is coupled to receive gas from supercharging means. 5.A reciprocatory machine according to claim 4 wherein said superchargingmeans is mounted to be driven by gases from said exhaust port andthereby comprises turbocharging means.
 6. A reciprocatory machineaccording to claim 1 wherein at least one of the valve means comprises asleeve valve.
 7. A reciprocatory machine according to claim 6 whichcomprises a pair of opposed pistons reciprocable within the workingchamber and the valve means comprises two separate sleeve valvesreciprocable about the pistons.
 8. A reciprocatory machine according toclaim 7 wherein said separate sleeve valves are reciprocable about therespective said pistons.
 9. A reciprocatory machine according to claim 8further comprising respective displaceable means for the two pistons,and wherein the sleeve valves are reciprocable by separate drive meansfrom the respective displaceable means.
 10. A reciprocatory machineaccording to claim 7 wherein said displaceable means are directlydrivingly coupled by an internally toothed belt.
 11. A reciprocatorymachine according to claim 1 wherein the displaceable means comprisesone or more crankshafts.
 12. A reciprocatory machine according to claim7 wherein the sleeve valves are arranged to reciprocate bothlongitudinally and circumferentially.
 13. A reciprocatory machineaccording to claim 12 wherein the stroke of circumferentialreciprocatory motion of each sleeve valve is at least 20% of the strokeof the longitudinal reciprocatory motion.
 14. A reciprocatory machineaccording to claim 1 further including ignition means operable in saidworking chamber whereby the machine comprises an engine.
 15. Areciprocatory machine according to claim 14 configured for 2-strokeoperation.